[en] To explore seismic behavior of blind bolted concrete-filled steel tube (CFST) frames infilled with precast sandwich composite wall panels (SCWPs), a series tests of blind bolted square CFST frames with precast SCWPs under lateral low-cyclic loading were conducted. The influence of the type of wall concrete, wall-to-frame connection and steel brace setting, etc. on the hysteretic curves and failure modes of the type of composite structure was investigated. The seismic behavior of the blind bolted CFST frames with precast SCWPs was evaluated in terms of lateral load–displacement relation curves, strength and stiffness degradation, crack patterns of SCWPs, energy dissipation capacity and ductility. Then, a finite element (FE) analysis modeling using ABAQUS software was developed in considering the nonlinear material properties and complex components interaction. Comparison indicated that the FE analytical results coincided well with the test results. Both the experimental and numerical results indicated that setting the external precast SCWPs could heighten the load carrying capacities and rigidities of the blind bolted CFST frames by using reasonable connectors between frame and SCWPs. These experimental studies and FE analysis would enable improvement in the practical design of the SCWPs in fabricated CFST structure buildings.

[en] A test rig with multi-functional purposes was specifically designed and manufactured to study the behavior of multi-planar welded tubular joints subjected to multi-planar concurrent axial loading. An experimental investigation was conducted on full-scale welded tubular joints with each consisting of one chord and eight braces under monotonic loading conditions. Two pairs or four representative specimens (two specimens for each joint type) were tested, in which each pair was reinforced with two kinds of different internal stiffeners at the intersections between the chords using welded rectangular hollow steel sections (RHSSs) and the braces using rolled circular hollow steel sections (CHSSs) and welded RHSSs. The effects of different internal stiffeners at the chord–brace intersection on the load capacity of joints under concurrent multi-planar axial compression/tension are discussed. The test results of joint strengths, failure modes, and load–stress curves are presented. Finite element analyses were performed to verify the experimental results. The study results show that the two different joint types with the internal stiffeners at the chord–brace intersection under axial compression/tension significantly increase the corresponding ultimate strength to far exceed the usual design strength. The load carrying capacity of welded tubular joints decreases with a higher degree of the manufacturing imperfection in individual braces at the tubular joints. Furthermore, the interaction effect of the concurrent axial loading applied at the welded tubular joint on member stress is apparent.

[en] In the periodic repainting of steel bridges, often the steel surface has to be prepared by using power tools to remove surface contaminants, such as deteriorated paint film and rust, and to increase the adhesive strengths of the paint films to be applied newly. Surface preparation by bristle roll-brush grinding, which is a type of power tool, may additionally introduce compressive residual stress and increase the fatigue resistance of welded joints owing to the impact of rotating bristle tips. In this study, fatigue tests were conducted for longitudinally out-of-plane gusset fillet welded joints and transversely butt-welded joints to evaluate the effect of bristle roll-brush grinding prior to repainting on the fatigue resistance of the welded joints. The test results showed that bristle roll-brush grinding introduced compressive residual stress and significantly increased fatigue limits by over 50%.

[en] A new type of earthquake-resisting element that consists of a steel plate shear wall with slits is introduced. The infill steel plate is divided into a series of vertical flexural links with vertical links. The steel plate shear walls absorb energy by means of in-plane bending deformation of the flexural links and the energy dissipation capacity of the plastic hinges formed at both ends of the flexural links when under lateral loads. In this paper, finite element analysis and experimental studies at low cyclic loadings were conducted on specimens with steel plate shear walls with multilayer slits. The effects caused by varied slit pattern in terms of slit design parameters on lateral stiffness, ultimate bearing capacity and hysteretic behavior of the shear walls were analyzed. Results showed that the failure mode of steel plate shear walls with a single-layer slit was more likely to be out-of-plane buckling of the flexural links. As a result, the lateral stiffness and the ultimate bearing capacity were relatively lower when the precondition of the total height of the vertical slits remained the same. Differently, the failure mode of steel plate shear walls with multilayer slits was prone to global buckling of the infill steel plates; more obvious tensile fields provided evidence to the fact of higher lateral stiffness and excellent ultimate bearing capacity. It was also concluded that multilayer specimens exhibited better energy dissipation capacity compared with single-layer plate shear walls.

[en] L-shaped columns composed of concrete-filled steel tubes (LCFST columns) connected by steel plates, which are important component to make sure the mono-column working together, were investigated under axial loading experiment with different width and thickness of connection plates. The relationships between load and longitudinal displacement, lateral displacement, longitudinal strains and transverse strains as well as failure mode are presented. Load carrying capacity of LCFST columns increased with the width and thickness of the connection plates increasing. In addition, the integrity of the specimen was improved with increase of thickness and decrease of width of the connection plates. Failure modes obtained from the finite element model were consistent with the phenomenon observed in the test. Besides, the parameters of slenderness ratio, dimensions of connection plate, and transverse stiffener spacing were analyzed. Finally, the calculating method of yield bearing capacity of axial compression was proposed based on the former analysis.

[en] This paper presents an analytical approach to predict the critical load of global buckling with locally buckled channel-section columns under axial compressive loads. The effect of local deformation before global buckling is considered. The analysis is performed by using the Rayleigh–Ritz method. The analytical solution is validated by using the nonlinear finite element analysis method. Parametric study is also performed for different sections including different values of slenderness ratio, height-thickness ratio and width-height ratio. The comparison between the present approach and those taken from Chinese and American standards demonstrates that the present model provides a good approach for predicting the critical loads of steel columns involving local and global buckling interaction.

[en] The proposed prefabricated bolted beam-to-column connection (BBCC) has been introduced to remove the problems of continuous/box columns and to show such merits as high-quality factory fabrication, easy transportation/erection/resumption, investment return, prefabrication, and modularization; this paper aims at designing and numerically studying the cyclic behavior of the novel designed connections. To this end, first the technical requirements and the design formulas are presented; three sample connection are designed; a similar connection was modeled, and the numerical and experimental results were compared and validated. Then, three design models were made to study the behavior of the exterior connections under cyclic load. The bases adopted for the model behavior were the AISC seismic provision requirements. The results show that all the AISC specific moment frame requirements including the failure mode, rigidity, ductility, moment capacity, rotational capacity, and ultimate rotation were met and the accuracy of design formulas are achieved.

[en] Repair process of structures after a strong earthquake is often governed by the level of permanent deformation experienced by these structures during the shaking event. These phenomena drastically affect the repair cost in addition to the prolonged time needed to accomplish this complex process. In this research the feasibility of utilizing the Re-centering capability of a dual system consisting of steel special moment resisting frame ‘SMRF’ and Inverted-Y geometric configuration eccentric braced frame ‘EBF’ to create an easy-repairable structure after a severe earthquake was examined. In this structural system a removable vertical shear link (i.e. using bolted connection) which is part of the EBF will act as a fuse to dissipate the earthquake input energy while the SMRF will act as a Re-centering system that will force the structure to return to its original position after removing the shear links by intentionally keeping it in the region of elastic behavior. The proposed system’s seismic performance was evaluated through performing series of pushover analyses under different loading patterns, and time history analyses under the action of seven earthquakes. Furthermore, the design provisions provided in the American Code “Seismic Provisions for Structural Steel Buildings” ANSI/AISC 341-10 were verified against the required response and extra recommendations for designing and detailing such structural system were introduced in order to achieve the required behavior. The performed study showed that during severe earthquakes the majority of the inelastic actions were localized within the shear links only while the SMRF behaved almost elastically with few exceptions. In addition, the study provided design and detailing recommendations to create an easy repairable structure after severe earthquakes.

[en] An investigation was conducted to evaluate the seismic behavior of a new type of steel box-section bridge piers with embedded energy dissipation shell plates. In this study, two sets of the new steel box-section bridge piers were designed and pseudo-static tests were carried out on ten steel box bridge piers under constant axial force, with a horizontal cyclic load on top of the piers. The change regularities of the failure mode, the patterns of local buckling, the load–displacement hysteresis curve and its curve skeletons, and the load-strain hysteresis curves of the specimens were analyzed. The rules of horizontal stiffener spacing on embedded shell plates, the axial compression ratio, the embedded shell strength, and the layout of longitudinal ribs in the box-section wallboards were obtained to evaluate their influence on the seismic behavior of the new-type steel piers. The test results indicated that, after installing the embedded shells, the deformation ability of steel box-section bridge piers was enhanced and their ductility was improved. The effects of axial compression ratio and the space of transverse stiffeners in embedded shells on the seismic behavior of the new steel piers were significant. When the space of the horizontal stiffeners on the embedded shells and the axial compression ratio become smaller, the bearing capacity and ultimate displacement capability of the specimens would be greater, the descent segment of the curve skeleton would be more gradual, and the deformability and ductility of the new-type steel piers would be better. The effects of setting longitudinal stiffening ribs and enhanced embedded shell strength on the bearing capacity and ductility of the steel box bridge piers were relatively small. Based on the experimental results, calculation equations were established for stable bearing capacity and maximum deformation of the new-type steel piers, under the constant axial force and horizontal cyclic loading, in order to promote their seismic design.

[en] The friction pendulum bearing (FPB) has been proved to be good isolation equipment, and the friction pendulum bearings were applied to K8 single-layer reticulated domes which span was 80 m. By using the vibration reduction analysis method based on the refine element models of FPBs, the seismic performance of the single-layer spherical reticulated domes with FPBs was studied and the influence of the column height and radius of section was discussed on the seismic performance of structures under the horizontal earthquakes. The results indicate that, with the increasing of height and radius of section of the supporting column, the vibration reduction effect of column supporting K8 single-layer reticulated domes with FPBs is enhanced first and then weakened. Under the horizontal earthquakes, the resonance phenomenon of K8 single-layer reticulated domes with column supports could be effectively avoided by the use of FPBs. For the cylindrical column supporting K8 single-layer reticulated domes with FPBs, compared with the corresponding hinge support structure, the vibration reduction effect of column support structure with FPBs which column height is 8 m is better when the column section radius is 0.50 m. However, the optimal column section radii are between 0.60 and 0.70 m when the column height is 10 m.